Power Considerations
Last Edit July 22, 2001
Step 7: Compute the Worst-Case Overhead Current
Multiply both the IEE and ICC overhead currents by the worst-case current
multiplier for the overhead current (WCCM3) to obtain the worst-case overhead
currents
IoverheadCCwc = WCCM3 * IoverheadCC
IoverheadEEwc = WCCM3 * IoverheadEE
Step 8: Sum the ICC and IEE Currents
Sum the internal macro, interface macro, and overhead worst-case currents,
keeping ICC and IEE separate to find the total IEE and ICC worst-case
currents
ICCwc = SUM IinternalCCwc + IinterfaceCCwc + IoverheadCCwc
IEEwc = SUM IinternalEEwc + IinterfaceEEwc + IoverheadEEwc
Step 9: Multiply by the Worst-Case Voltage
The worst-case voltage is dependent on whether the circuit is commercial
or military and the specified allowed power supply variations. The array
data sheet carries this information. The typical variation is shown below.
For commercial circuits, with a -5.2V or a +5V supply, the voltage variation
is usually ±5%. For commercial circuits using VEE = -4.5V, the variation
is ±7%
For military circuits, the voltage variation is usually ±10%. Note: The
worst-case voltage for the -4.5V supply as listed on the Q20000 data sheet,
where -4.5V supply varies ±7%. The worst-case voltage is taken as -4.8V
for military or commercial circuits
Table 7-14 Example Worst-Case Voltages
Nominal |
Commercial |
MILITARY |
+5.0V |
+5.25V |
+5.5V |
-5.2V |
-5.46V |
-5.72V |
-4.5V |
-4.8V |
-4.8V |
Multiply the worst-case DC current by the appropriate worst-case voltage:
PEEDC = IEEwc * VEEwc
PCCDC = ICCwc * VCCwc
This product is the worst-case DC power due to the macros on the array.
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